I seem to be the odd person when it comes to the distance my computer gives.
My rides are very consistent. I have certain points where I know the computer will click over to the next digit and it will be the same every ride, within a few feet.
But I've come across riders who get bigger numbers for the same territory. In fact, when we had the Honolulu Century, I showed less than 96 miles (might have been about 94). This struck me as a pretty big error!
Some time ago, I measured my wheel circumference very carefully. I sat on the bike while rolling it. I put a piece of tape on the tire to mark the spot more exactly (instead of using the valve stem which would be further away, possibly making eyeballing the result less accurate, and I did it repeatedly to be sure the number was always the same. Since then, whenever I get new tires, I don't measure it - I just do a normal ride and see if the numbers click over at the same key points (all are at least 9 miles away).
But with the century difference and a couple other cyclists I've checked with getting different numbers, I'm wondering who is right.
I think I am, because of the care I took, but also because I have some mapping software and also checked online at Google's gmap pedometer and they give virtually identical results to mine.
But I really don't know if these mapping sources are that accurate or not. Anybody know? They give figures to the hundredths so if they are accurate, then my computer is right.